The structural skeleton of a vehicle, typically made from welded sheet metal components, is generally referred to in the industry as a body-in-white (BIW), due to the sheet metal being initially coated in a rust retardant coating which is often white in color, prior to being painted the exterior color of the vehicle. It is also common in the industry for vehicle assembly plants to have flexible assembly lines which are capable of relatively quick changes to build different body style of vehicles to support production needs.
Multiple models of vehicle BIWs can be assembled in a “batch mix” or a “random mix”. In a batch assembly mix, all BIWs of a first type of vehicle model are assembled, then all BIWs of a second type of vehicle model are assembled, and so on. Assembling multiple models of vehicles in a batch mix can be advantageous because the number of tooling changes can be kept low, as a tooling change only needs to be undertaken when switching between assembling different models of vehicles. As an example, if there are seven different models of vehicles in a batch mix, six tooling changes are necessary to assemble all the vehicles in the batch mix assuming the tooling is initially set up for a first of the seven models.
In a random vehicle body assembling mix, the order in which BIWs for various models of vehicles are assembled is based on the color that the BIWs are to be painted. For example, a build that includes three different types of vehicle models, each of which includes vehicles of two colors, red and blue. In this example, bodies-in-white of a first type of vehicle model to be painted red are assembled, then bodies-in-white of a second type of vehicle model to be painted red are assembled, then bodies-in-white of a third-type of vehicle to be painted red are assembled. Next, a paint change is undertaken to change the color of paint to be applied from red to blue. After the paint change, bodies-in-white of the first type of vehicle model to be painted blue are assembled, then bodies-in-white of the second type of vehicle model to be painted blue are assembled, then bodies-in-white of the third-type of vehicle to be painted blue are assembled. Assembling different models of vehicle in a random mix can be advantageous because the number of paint changes can be kept low, as the number of paint changes can be one fewer than the total number of colors assuming the paint is initially set up for a first color.
Painting vehicles assembled in a batch build or assembly mix can be problematic because all bodies-in-white of a certain type of vehicle model are not typically painted the same color. One solution to this problem is to paint the bodies-in-white in the order in which they are assembled and to change the color of paint as necessary. However, this solution requires a large number of paint changes, and paint changes are time consuming and expensive.
Further, assembling vehicles in a random mix can be problematic because a large number of tooling changes are typically required. For example, the number of tool changes increases as the number of paint colors increases. The number of tooling changes required for a random mix is approximately equal to the total number of colors multiplied by the number of vehicle models.